[feat ]: leetcode 2370

Signed-off-by: Bo-Wei Chen(BWbwchen) <tim.chenbw@gmail.com>

Author: BWbwchen

leetcode/2370_Longest-Ideal-Subsequence.cpp

@@ -0,0 +1,22 @@
+class Solution {
+public:
+    inline bool valid(char a, char b, int k) {
+        return abs(a - b) <= k;
+    }
+    int longestIdealString(string s, int k) {
+        int n = s.size();
+        vector<int> dp(26, 0); // a ~ z
+
+        for (auto c : s) {
+            int tmp = std::numeric_limits<int>::min();
+            for (char j = 'a'; j <= 'z'; ++j) {
+                // dp[c] = max_j(dp[j]) + 1, where valid(j, c, k) == true
+                if (valid(j, c, k))
+                    tmp = max(tmp, dp[j-'a']);
+            }
+            // Why use tmp? Because we can not update the dp[c-'a'] and compare it simultaneously.
+            dp[c-'a'] = max(dp[c-'a'], tmp + 1);
+        }
+        return *max_element(dp.begin(), dp.end());
+    }
+};